Heat transferring tube structure



Feb. 1, 1938. EVANS I 2,107,031

HEAT TRANSFERRING TUBE STRUCTURE Filed April 29, 1936 i INVENTOR, Gerda/7 M 5 4 75 ATTORNEY.

Patented Feb. 1, 1938 UNITED STATES PATENT OFFICE Application April 29,

serum.

The subject matter of this invention lies in the heat exchange art, and it has to do particularly with a structure in the nature of a conduit or tube, constructed to effect heat exchange from one fluid to another.

The principal object of the invention is the provision of a structure in the nature of a tube having heat conducting and radiating parts, and which provides for efilcient heat conduction from a fluid within the tube to a fluid without the tube. To this end the invention contemplates a tube advantageously made of sheet metal stock, some portions of which are fashioned to form the conduit or tube walls, and other portions of which are so disposed as to provide heat conducting members for directly conducting heat from the inside to the outside of the tube, or vice versa. It may be pointed out that finned tubing has heretofore been used for heat conducting purposes wherein fins are applied to the outside of the tube. A joint is formed where this attachment is made, and wherever such a joint occurs there is a resistance to conduction of heat. In accordance with the present invention heat conducting members of integral structure have surfaces extending within the tube and surfaces projecting outside the tube, so that there is a direct path having no joints for the conduction of the'heat.

A further object of the invention is to provide a heat transfer structure of the type mentionedwhich can be made in indefinite lengths from strip stock and which, upon completion, embodies heat transfer areas or fin areas integrally embodied in the tube structure. Therefore, no additional operations are necessary to equip the structure with fins or other heat transferring devices.

The tube of this invention may, of course, be used for various heat exchange purposes. and may be made up into heat transfer devices for different uses. Some of such uses are as follows: radiators for internal combustion engines; condenser units for refrigerators; evaporator units for refrigerators; various other kinds of radiators such as hot water heaters for automobiles, and heat exchange devices for air conditioning apparatus, etc.

In the accompanying drawing:

Fig. 1 is an elevational view of a length of tube constructed in accordance with the invention and fashioned into several runs of a coil.

Fig. 2 is a view illustrating the cross sectional shape as would be seen on line 2-4 of Fig. 1 and showing the structure in perspective.

Fig. 3 is a perspective view of a modified form of the invention.

1936, Serial No. 76,903

Fig. 4 is a cross sectional view of somewhat enlarged form, showing a further modified form of the invention.

The structure, as shown in Fig. 2. is formed of a plurality of sheet metal strips. One of the strips is fashioned with a central portion I generally of semi-circular shape with opposite edges 2 and 3. Between the central portion and the edges are intermediate zones which may be of a relatively fiat nature as at 4. There is another similar strip positioned in a reverse manner having; its central portion as at 5, opposite edges 6 and I, and intermediate parts 8. These lengths of sheet metal are disposed in opposing relation with the semi-circular parts defining a hollow cross sectional form.

Other members for heat transfer purposes may be employed, and as shown in Fig. 2 there are two of such members or strips. One of these is shown at ill with its intermediate portion located between the zones 4 and 8 of the two opposed strips, with one edge Ii located outside the tubular form, and the other edge portion I! located within the hollow cross sectional form. The portion I! may be suitably fashioned into irregular form, if desired; as shown in Fig. 2 the inward edge l2 extends at an angle to a diametrical line across the hollow cross sectional form, has a bend line i3, and has its extreme end it extending at an angle toward the diametrical line. The diametrical line referred to is a line paralleling the portions 4 and 8. The other heat transferring member is shown at i5 having one edge i6 outside the tubular form and the other edge I! within the same, and it may be similarly fashioned with a bend line l8 and an angularly disposed extreme end portion 20.

This tube-like structure is to be united at seams along the portions 4 and 8, which are in abutting relation with each other, with the members I 0 and i5 interposed therebetween. Such seams are designed to be fiuid tight, with the result that a sealed tubular form is provided. The seams may be provided in a number of ways; for example, the overlapping parts 4 and 8, with the interposed intermediate portions of the pieces ill and I5, may be welded together. This may be accomplished by passing the form between roller electrodes of a welding machine.

.Such a structure may be made by a substantially continuous process by drawing the several strips from supply rolls, passing them through forming rollers, then fitting them together substantially as shown in Fig. 2, at which time the completed assembly may be run through opposed welding rolls for establishing the weld connections. Tube forming machines for handling strip stock of this nature are well known to those versed in the art, and also welding machines embodying roller electrodes are well known to those versed in the art, and the details of these machines need not be gone into in this case. Suffice it to say that alternating current may be used in making the weld, with each pair of opposed electrodes engaging the portions 4 and 8; and the speed of movement of the assembled strips may be coordinated with the frequency of the alternating current so that the successive impulses are sumciently close together to provide a fluid tight welded seam on opposite sides of the tube structure.

The seams, however, may be made by the use of a molten sealing metal. For example, the strips of stock, either all or some of them, may be plated with tin or a so called solder such as a tin and lead alloy, and suflicient heat may be applied to the portions 4, 8 and the intermediate parts of the members l and i to melt the coating metal on these portions and sweat the contacting parts together.

Furthermore, it will be noted in Fig. 2, that the extending parts 3 and 'l on one side of the tube are angularly disposed with respect to the extending part i l. Likewise the extending parts, or wings 2 and 6, are angularly disposed with respect to the extending part 16. This is for the purpose of providing free access to these parts of the ambient atmosphere or other liquid or fluid around the outside of the tube. Thus a large area is provided for transferring heat to or from such fluid. In initially making the structure the angularly disposed parts 2, 3, 6 and I may lie flush against the parts I 6 and it until after the seam is completed, whereupon these angularly disposed parts may be bent into proper position. On the other hand, these angularly disposed parts may be so angularly disposed before the seam is made.

In Fig. 3 a structure is shown similar to that of Fig. 2, and in general the same reference characters are applied. However, some of the parts are split and bent to form wings to provide for some increased agitation in the ambient fluid. To this end the wing corresponding to the wing 2 of Fig. 2, is cut crosswise to provide wings 2a and 2b, which are bent so as to occupy different planes. The other external parts corresponding to the wings 3, 5 and i may be similarly cut and fashioned, as shown, the reference characters being the same, except for the additional characters a and b. In the particular form shown in Fig. 3, the interior portions l2 and I! have been left straight, except for an angular disposition, although this structure is not essential to the cutting of the exterior parts to form the separate wings.

A further modified form is shown in Fig. 4, and this form provides additional radiating surfaces both inside and outside the tubular structure. In this form there are four similar parts each forming a segment of the tube wall. Each part has an intermediate portion which may be so curved as to provide a tube of circular form, and the portions have opposite radiating projecting edges 26 and 21. The portions have intermediate parts 28 between their intermediate portions and edge parts for disposition in close proximity and in substantially abutting relation. However, between these abutting parts 28 are disposed other heat conducting and radiating members. There are four of these members shown, and they may all be similar and may comprise each a sheet metal body having an outer edge 30 and an inner edge 3|. Those portions which lie within the tubular form may be offset, as shown at 32, so that the portions will clear each other within the tube and preferably divide the tube into a more or less symmetrical arrangement. This form is completed by sealing the seams where several layers overlap, as at 28, which may be done by welding or by uniting the overlapping parts by a molten sealing metal which may be carried into place in the form of a plating or coating upon the strip stock, or otherwise provided.

Such tubular structure, as pointed out above, may be used in various heat exchange devices. As an example, a length of such tube is shown in Fig. l fashioned into straight runs 40 with bends 4| connecting the same, and such a device composed of a number of such runs may, for example, be used as a condenser for a refrigerator. In making such a structure the external wings may be cut inwardly substantially to the seam shown at 42 so that these projecting wings may be spread apart in angular relation on the straight runs, but allowed to lie in close overlapping relation at the bends.

A heat transferring structure of this type may be used advantageously in the evaporator structure of a refrigerator, particularly of the socalled flooded type. In this case the body of the evaporator may include a number of such tubular forms, and, of course, as is well known to those versed in the art, the flooded type of evaporator is partially filled with liquid refrigerant. In such a case the internal members l2, l1 and 3| may be of relatively rough formation, that is to say the edge portions may be left sharp where the metal is cut, and the surfaces of these parts may not be polished smooth. Thus the liquid refrigerant comes into contact with these surfaces to facilitate the action of ebullition. The globules of gas may cling-to and form on such surfaces until they grow to sufficient size to cause them to become free of surfaces and rise to the surface of the liquid refrigerant. To further facilitate ebullitlon, or to further facilitate transfer of heat from the fluid within the tube to the conducting portions, the inner sheet metal parts projecting into the tube may be lanced to form wings, with the wings bent into different planes, as illustrated at in Fig. 4. This lancing and bending of the wings is similar to the lancing and bending of the wings 2a and 2b shown in Fig. 3. Also, it will be appreciated that this internal lancing arrangement and bending to form wings may be applied to the parts l2 and ll of the form shown in Figs. 2 and 3. Likewise, it is within the invention to lance and bend the external radiating portions such as the parts 3, l, H and others, in the form shown in Fig. 2, and the parts 26, 21 and 30 in the form shown in Fig. 4.

In all cases where the device is used for heat transfer purposes it will be noted that there is an efficient heat conducting path from the inside of the tube to the outside thereof, or vice versa. For example, where there is a liquid within the tube to be cooled, the heat of the liquid is transferred to the inwardly projecting parts, which are integral with the radiating fins ll, I6, and 30. Thus there is a direct integral metallic path for conducting the heat away from the liquid, and it is not necessary for the heat to be conducted across a joint. Also, the heat of the liquid which is transferred into the wall portions of the tube I. 5 and 25, may be conducted directly into the radiating fins integral therewith, such as the fins 2 and 3 integral with the wall member I. sealed by molten metal the heat does not need to be transferred across this seam, but in fact may be conducted directly through the seam by the integral metal. It will be understood that this structure may be made of any suitable heat transferring material, preferably metal. The stock used may be sheet steel, copper, or aluminum, or other metal, and where the seams are to be formed by a molten sealing metal, such molten sealing metal should have a melting point lower than that of the sheet stock forming the body of the structure, which, of course,.would be the case where tin or an alloy of tin and lead is used with a base metal structure of steel, copper or aluminum.

I claim:

1. A tube structure for heat transfer purposes comprising, a plurality of longitudinally drawn strips of sheet metal extending lengthwise of the structure, each strip having an intermediate portion for constituting a part of the tube wall, said intermediate portions being disposed so that the portions cooperate to form a complete tube wall, the edges of the strips extending outwardly of the tube form to provide radiating parts, each strip having an abutting portion between its intermediate portion and each edge, with the abutting portions of one strip substantially facing the abutting portions of another,,and a plurality of other strips of the same length as the first mentioned strips, one positioned between each two adjacent abutting portions of the first mentioned strips and each lying in part within the tube and in part without the tube to provide unbroken heat conductors within the tube and radiating parts without the tube, said abutting portions and the parts of the other strips lying therebetween being united to seal the tube and hold the strips in assembly some of said radiating parts being cut transversely of the tube to form wings, and alternate wings on each cut radiating part lying in different relatively angular planes.

2. A tube structure for heat transfer purposes comprising, a plurality of longitudinally drawn strips of sheet metal extending lengthwise of the structure, each strip having an intermediate portion for constituting a part of the tube wall, said intermediate portions being disposed so that the portions cooperate to form a complete tube wall, the edges of the strips extending outwardlyof the tube form to provide radiating parts, each strip having an abutting portion between its intermediate portion and each edge, with the abutting portions of one strip substantially facing the abutting portions of another, and a plurality of other strips of the same length as the first mentioned strips, one positioned between each two Even where the seams are adjacent abutting portions of the first mentioned strips and each having an edge within the tube and an edge without the tube to provide unbroken heat conductors and radiating surfaces, said abutting portions and the parts of the other strips lying therebetween being united by molten sealing metal to seal the tube and hold the strips in assembly said edges of the said other strips which lie within the tube lying in different planes and extending beyond the center of the tube in overlapping relation 3. A tube structure for heat transfer purposes comprising, a pair of sheet metal strips each having a central curved portion, securing parts on each side of the curved portion, and edge portions extending from the securing parts, said strips being disposed in opposed relation with the securing parts adjacent each other and with the central portions forming a tube, and a pair of other strips, one between the opposite securing parts of the first mentioned strips, and each having a portion lying within the tube and extending substantially to the median line of the tube and an edge portion lying without the tube, the securing portions and the second mentioned strips being secured together to seal the tube and hold the strips in assembly, and the several said edge portions of all the strips being angularly disposed with respect to each other to provide spaced radiating surfaces.

4. A tube structure for heat transfer purposes comprising, four similarly formed metal strips each having an intermediate portion, contacting parts on opposite sides of the intermediate portion, and projecting edge portions, said strips being disposed in complementary relation so that the intermediate portions form a tube, a plurality of other sheet metal strips, one lying between each two opposed contacting portions of the first mentioned strips and each having one edge part within the tube and one edge part without the tube, said contacting portions and the sheet metal strips therebetween being united to seal the tube and hold the strips in assembly.

5. A tube structure for heat transfer purposes comprising, four similarly formed metal strips each having an intermediate portion, contacting parts on opposite sides of the intermediate portion, and projecting edge portions, said strips being disposed in complementary relation so that the intermediate portions form a tube, a plurality of other sheet metal strips, one lying between each two opposed contacting portions of the first mentioned strips and each having one edge part within the tube and one edge part without the tube, said contacting portions and the sheet metal strips therebetween being united to seal the tube and hold the strips in assembly, the edge portions of the first mentioned strips and the outside edge portions of the second mentioned strips being angularly disposed with respect to each otherto provide spaced radiating surfaces.

GORDON M. EVANS. 

